A fuel cell is a device that generates electricity by a chemical reaction. Among various fuel cells, solid oxide fuel cells use a hard, ceramic compound of metal (e.g., calcium or zirconium) oxide as an electrolyte. Typically, in the solid oxide fuel cells, an oxygen gas, such as O2, is reduced to oxygen ions (O2) at the cathode, and a fuel gas, such as H2 gas, is oxidized with the oxygen ions to from water at the anode.
Interconnects are one of the critical issues limiting commercialization of solid oxide fuel cells. Currently, most companies and researchers working with planar cells are using coated metal interconnects. For example, ferritic stainless steel based metal interconnects, such as Crofer 22 APU, and powder metallurgy formulations from Plansee AG in Austria, have good CTE (coefficient of thermal expansion) mismatch and good compatibility with solid oxide fuel cells. However, oxidation of metal interconnects during operation, thereby forming metal oxides, such as Cr2O3, and subsequent migration of metals of the metal oxides (e.g., chromium migration) to an electrode layer and/or electrode-electrolyte interface is one of the primary mechanisms leading to performance degradation in solid oxide fuel cells.
While metal interconnects are relatively easy to fabricate and process, they generally suffer from high power degradation rates (e.g. 10%/1,000 h) partly due to formation of metal oxide, such as Cr2O3, at an interconnect-anode/cathode interface during operation. Ceramic interconnects based on lanthanum chromites (LaCrO3) have lower degradation rates than metal interconnects partly due to relatively high thermodynamic stability and low Cr vapor pressure of LaCrO3 compared to Cr2O3 formed on interfaces of the metal interconnects and electrode. However, doped LaCrO3 generally suffers from dimensional changes, such as warping or some other forms of distortion, and consequent seal failures in reducing conditions. Another issue related to LaCrO3 is its relatively low sinterability.
Therefore, there is a need for development of new interconnects for solid oxide fuel cells, addressing one or more of the aforementioned problems.